Electric controlling apparatus



J. L. SCHERMERHORN.

ELECTRIC CQNTROLLING APPARATUS. H APPLICATION FILED AUG 2.1920.

4 SHEETS-SHEET 1- v (jwventoz J. L. SCHERMERHORN.

ELECTRIC CONTROLLING APPARATUS.

AFFLICATIOLN FILED AUG. 2. 1920.

1,399,084, Patented Dec. 6, 1921.

4 SHEETSSHEET 2.

J. L. SCHERMERHORN.

ELECTRIC CONTROLLING APPARATUS.

APPLICATION FILED AUG-2, 1920.

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J. L. SCHERMERHORN' ELECTRIC CONTROLLING APPARATUS.

APPL CATION FILED AUGv 2. I920.

' Patented Dec. 6, 1921.

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UNITED STATES PATENT OFFICE.

JOHN L. SCHERMERHORN, OF NEWARK, NEW JERSEY, ASSIGNOR T0 AMERICAN TRANSFORMER COMPANY, OF NEWARK, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC CONTROLLING APPARATUS.

Specification of Letters Patent.

Patented Dec. 6, 1921.

Application filed August 2, 1920. Serial No. 400,725.

To all whom it may concern:

' Be it known that 1, JOHN L. SCI-IERMER- HORN, a citizen of the United States of America, residing at Newark, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Electric Controlling Apparatus, of which the following is a specification.

This invention relates to switching devices or controllers for varying the electric potential or current strength in a part or parts of an electric system, and more particularly to effect variations of voltage or current by small increments over a relatively wide range.

It is adapted for application to either a direct current system or to an alternating current system, and, if the latter, to either a single phase or to a polyphase system.

As applied to a. single phase system, for example, the invention may comprise a twoswitch controller for a transformer, although one involving three or more switches would fall within the purview of the invention. When so used, certain of the transformer taps may divide a small portion of the transformer winding into a plurality of relatively small subdivisions, so that any two of the successive taps may differ in potential by a small increment of any desired magnitude. The remainder of the transformer winding may be divided by other taps into larger subdivisions such that successive taps of the larger subdivisions differ in potential by correspondingly larger increments, each of which may, if desired, be equal or substantially equal to the sum of the potential difference between the first and the last of the taps of the smaller subdivisions. In the preferred form herein disclosed there are nine of the smaller subdivisions and nine of the larger subdivisions, the difi'erence of potential of each of the larger subdivisions equaling ten times that of one of the smaller subdivisions.

The taps from the smaller subdivisions may be connected to contacts in a multiple contact switch, which, as a matter of convenience, may be termed a primary switch, and those from the larger subdivisions may be likewise connected to contacts of another multiple contact switch which may be designated a secondary switch. The tap separating the smaller subdivisions of the transformer winding from the larger may be connected to a contact of each switch which mary be regarded as its zero contact.

' ccording to the invention herein disclosed, the primary switch has an arm or wiper which may be moved from contact to contact in order to cut the smaller subdivisions of the transformer winding into a circuit, one after another, and said switch is capable of repeating its cycle of move ment one or more times in succession. ldeans is also provided whereby at the completing step of a cycle of movement by the primary switch, the secondary switch will be moved one step so as to cut one of the larger subdivisions of the transformer winding into the same circuit. At the step of the primary switch by which this is effected, all of the small subdivisions of the transformer winding will be out of the circuit. The primary switch may then be moved through a second cycle of movement, again cutting in small subdivisions without further operation of the secondary switch, until the second cycle is completed, as which time the small subdivisions will be again cut out and a second large subdivision cut in. This may be continued until the whole transformer winding is included in the circuit.

hen applied to a continuous current system a resistance element may be connected between points of different potential in place of the transformer winding, and subdivided by conducting wires corresponding to the transformer taps above referred to. These wires may be led to the contacts of the primary and secondary switches by which the system may be controlled in the manner above described.

If applied to a polyphase, system, as for example, a three phase system, there may be provided three separate sets of transformer windings, one set for each phase, each subdivided in the manner abovedescribed. There will also be provided for each phase a primary and a secondary switch having contacts connected 'with the transformer taps of the corresponding transformer winding. When so used the three primary switches will be connected by gearing so as to move their switch arms to corresponding switch contacts in unison. The secondary switches will be likewise connected and for-the same purpose. There will also be a driving connection whereby on movement of each of the primary switch arms through the last step of its cycle of movement, the secondary switch arms will each be advanced one'step.

Heretofore, in controller switches of the above mentioned type, an auxiliary switch arm has been provided to engage an approached contact before the main switch arm breaks its connection with a contact from which it is being moved and the said main and auxiliary switch arms are connected through a current limiting element, comprising resistance or impedance, so as to provide means for passing from one contact to another without either breaking the circuit or short circuiting the subdivision of the transformer winding between the taps leading to said contacts.

According to the present invention means is also provided for causing the connection between said main and auxiliary arms to be effected through a current limiting element of a materially greater capacity when the switch is caused to make the last step of its cycle of movement, at which time the difference of potential between the bridged contacts is equal to that of the sum of all the subdivisions of the transformer winding controlled by the switch.

If desired, each switch may be provided I with such means for adding resistance or impedance of relatively larger capacity, on making the last step of its cycle of movement, in which case, after continuing the rotation of the primary switch .until the switch arm of each switch rests upon the last contact of its respective series, the total electromotive force, thus cut into circuit, may be cut out by a single advance step of the primary switch which, in returning to its initial contact will, at the same time, advance the secondary switch toflits initial contact, without short circuiting any of the subdivisions of the transformer winding.

The primary switch may be manually moved from contact to contact by means of a suitable handle or crank'arm, or a motor may be employed for the purpose. As a part of such motor driving means the invention .includes means, rendered effective whenever the motor is set in operation, to prevent it from stopping when the switch arms are in an intermediate position bridging two contacts, or in any position in which the main switch arm does not rest in a centered relation with aswitch contact. Such means is adapted for application to either an alternating current motor or to a direct current motor, and the improved motor control is adaptedfor use in connection with any multipoint switch.

adapted for application to devices involving drum controllers, sliding switches, or any switch which operates in steps.

In the accompanying drawings, illustrating the invention in its preferred form, as

well as certain modifications thereof:

Figure 1 is a diagram showing the invention embodied as a controller for a single phase alternating current transformer.

Fi 2 is a section through the controller switc es at the line 2-2, Fig. 1, looking in the direction of the arrows.

Figs. 3 to 6 inclusive are diagrams showing different positions of the switch arms when passing from the zero contact to the next contact in advance.

"Figs. 7 to 9 inclusive are diagrams illustrating different positions of the switch arms when passing from the last contact of the series back to the zero contact.

Fig. 10 illustrates the invention as embodied in a controller for a 3 phase alternating current transformer.

Fig. 11 is a face view of part of a switchboard structure for the controller illustrated in Fig. 10, showing the threeprimary switches.

Fig. 12 is a side view of the same part of said switchboard structure, illustrating the gearing by which the various switches are connected. Fig. 13 is a diagram illustrating a motor drive for the controller switchesand the connections by which the motor is prevented from coming to rest when a switch arm bridges two contacts, or is not in a centered relation with a contact.

Referring more particularly to Fig. 1, illustrating the invention, as applied to a controller for a single phase alternate current transformer, P represents the primary switch, and S the secondary switch, by which the electromotive force of a circuit may be controlled. As disclosed in said figure, 101 -102 may represent the incoming leads from any suitable source of electromotive force. These leads may be connected by the switch 103 to contacts 104-105, leading by way of conductors 106-107 to the terminals 108-109, of an auto-transformer designated generally by the reference character 110 As herein disclosed, a relatively small porthe last mentioned taps step-up transformer 120,

tion of the winding of the transformer 110 is divided into 9 small subdivisions by trans former taps designated by reference characters 0 to 9 respectively. These subdivisions may be of such size that the respective transformer taps O to 9 may differ from each other in potential by increments of any desired magnitude. The remainder of the transformer winding may be divided into larger subdivisions by transformer taps 10, 20, 30, etc., to 90 inclusive, and the portion of the transformer winding between each of may be such that the difference of potential between successive taps will be 10 times that between any two adjacent taps leading from the smaller subdivisions.

Each of the switches, P

and S, is provided with a series of contacts 111, secured to the face of the panel board, a portion of which is indicated at 112. As herein disclosed, there are 10 such contacts in each switch, the same being arranged in a circle.

tact of each switch, which may be subdivisions from the smaller subdivisions. ing 9 contacts f the primary switch are connected respectively with the transformer taps 1 to 9 inclusive in the order indicated, and may therefore be referred to as the 1 contact 2 contact, etc., respectively.

Likewise the remaining 9 contacts of the secondary switch are electrically connected with the transformer taps 10, 20, 30, etc., to 90 inclusive, in the orderindicated. These contacts may, therefore, be referred. to as the 10 contact, 20 contact, etc.

he primary switch P has a main switch arm 113 fast upon a shaft or spindle 114, rotatively mounted in the panel board, and the secondary switch S has a like main switch arm .115, fixedly secured to a like spindle 116. These switch arms 113 and 115 may be connected by conductors 117118 to the terminals of the primary winding 119 of a the secondary winding of which is indicated at 121.

When the switches are in the positions indicated, with the main switch arms resting on the zero contacts, the transformer 120 will not be energized even though the auto-transformer 110 is connected to the terminals of the supply circuit by closing the switch 103, since both terminals of the primary winding 119 are connected through said switch arms with the zero tap of the auto-transformer. It will be apparent, however, that on the rotation of the arm 113 of the primary switch P in a clockwise direction from contact to contact, one after another of the small subdivisions of the auto transformer 110 will be cut into circuit with the primary winding 119 of the transformer also provides to prevent overthrow 120. Likewise, on rotating the switch'arm 115 of the secondary switch in a counter clockwise direction from contact to contact,

ing 119 will at all times equal the sum of the increments of potential of all of the subdivisions, large and small, of the winding 110, which have been cut into circuit by the two switches.

In order that the difference of potential across the terminals of the winding 119 may be gradually increased from zero to the total difference of potential of the auto-transformer by small increments, each equal to the difference of potential of one of the smaller subdivisions of the winding 110, the invention provides means whereby the smaller subdivisions may be cut in, one after another, in succession, and then all cut out, concomitantly with the cuttin in of one of the larger subdivisions. T e invention means whereby such operation may be repeated until the whole winding of the auto-transformer has been cut into circuit with the winding 119. To this end the spindle 114 of the primary switch has fast thereon a wheel 122 having a tooth 123, adapted once in each revolution to engage a notch 124 in a wheel 125, fixedly attached to the spindle 116 of the secondary switch.

As herein disclosed thewheels 122]25 when moved by the tooth 123. e invention, however, is not limited tothis specific driving connection, since all that is essential is to provide means whereby the switch arm of the secondary switch will be advanced one step whenever the primary switch arm is advanced from its 9 contact to its zero contact. When the Geneva gears are not used, however, it may be necessary to provide a detent device of any appropriate type of the wheel 125, and to normally hold it in a position in which its switch arm is centered on a switch contact.

As is customary in the construction of switches of the above mentioned character, means may be provided whereby, on movement of the switch arm from one contact to another, neither cause the circuit controlled thereby to be broken, nor the subdivisions of the transformer connected with the switch contacts to be short circuited. To this end each of the switch arms is provided with a secondary switch arm 126, separated therefrom, but secured thereto, by a fastening element of insulating material 127. The outer end of each arm 126 is I trical connection with the adapted to be brought into successive electric connection with the respective contacts.

adapted to make contact with a curved conducting plate 128, secured to the face of panel board. The plate 128 of the primary switch is electrically connected with the conductor 117 through a resistance or impedance 129. The corresponding plate 128 of the secondary switch is likewise connected withthe conductor 118 by a resistance or impedance 130.

The function. of the auxiliary switch arm and the resistance through which it is connected with the main switch arm may be readily described in connection with Figs. 3 to 6 inclusive, of the drawings, illustrating the different positions of the primary switch.

In Fig. 1' the main switch arm of the primary switch is illustrated as resting upon the zero contact. In Fig. 3 the switch arm is illustrated as having been moved until the auxiliary arm has been brought into elec- 1 contact but the main switch arm has not yet broken its connection with the zero contact. In this posi ion the circuit may still be traced from the zero transformer tap through the zero switch contact, to the main switch arm and thence to wire 117. At the same time the first of the small subdivisions 0 the transformer winding 110, is shunted by. the two switch arms and the resistance by whic they are connected. In Fig. 1 the main switch arm is indicated as having been moved sufficiently far to break its connection with the zero contact and the auxiliar arm is centered with the 1 contact. In t 's position the circuit must be traced from the transformer tap 1 through the auxiliary switch arm conducting plate 128 and resistance 129 to conductor 117. thisstage the first of the smaller subdivisions of the winding 110 has been cut into circuit with the winding 119 of transformer 120 but the resistance 129 is also included.

As illustrated in Fig. 5 the main switch arm-and auxiliary switch arm are both illustrated as being in electrical connection with the 1 switch contact, thereby resistance 129 out of the circuit, be traced directly from transformer tap through said contact to the main switch arm and thence to conductor 117.

Fig: 6 illustrates the positions of the switch arms after one complete step has been efiected, the main switch arm being centered on the 1 switch contact and the auxiliary switch arm resting on the insulation between the 1- and the 2 contact. By properly apportioning resistance 129, with respect to the electromotive force of the small transformer switc v subdivisions the electromotive force of the maybe gradually in-' controlled circuit abrupt variation in po- The inner end of each arm is invention, the switches are mten 1 from the 9 switch contact mes es tential as the switch arms pass from one conh tact-to another of the switch.

The effect of the auxiliary arm 126 and resistance 130 of the secondary s itch is the same as that of the primary switch, the resistance or impedance 130 being properly apportioned to the relatively larger subdivisions of the transformer winding 110 'which are shunted thereby from time to time during operation of the switch.

If, as is contemplated as a feature of this ded to be in the same direction rotated continuousl f more than 360 degrees,

through an angle 0 and if the means to be relied upon to prevent the short circuiting of the transformer windings, an t e opening of the circuit, throughout the comlete movement of the-switch, the resistance 129 for the primary switch would be connected in shunt with the whole series of small transformer subdivisions between the zero tap and the 9 tap whenever the switch arms are caused to bridge the two contacts connected to said taps on movement from the, 9 switch contact back to the zero contact. Since the restistance 129 must be of a magnitude apportioned in accordance with the electromotive force of but one of the small subdivisions of the transformer, it would be inadequate to prevent a marked drop of potential when bridged across all 9 of these subdivisions. According to the herein disclosed invention, this ditficulty is overcome in the following manner p The curved conductor 128 is -co 'tructed in the form of a ring, havin a section 131 (see Fig. 6) separated and insulated from the main ortion 128. This section is connected wit the conductor 117 through a resistance or impedance 132, which may int clude the resistance or impedance 129 and which may bear the same proportion to thetotal number of small subdivisions of the transformer winding that the resistance or impedance 129 bears to one of said subdivisions. The conducting section 131 is so positioned with respect to the switch contacts that the inner end of the auxiliary switch arm will be brought into contact therewith before the main switch arm is separate when it is being moved therefrom to the zero contact. During this stop of the switch movement, therefore, the larger resistance or impedance 132 will be comiecte'd in shunt with the total series of small subdivisions of the transformer winding when the two contacts last mentioned are bridged b the main and auxiliary contact arms. '1 is is illustrated in Figs. 7, 8, and 9. v

In Fig. 7 the main switch arm rests uponthe 9 switch contact and the inner end 0 the auxiliary arm rests upon the conductor 131. At this time theiircuit from trans- 13( heretofore described were so former tap 9 to conductor 117 may be traced through the 9 switch contact and the main switch arm 113.

Fig. 8 shows the switch in the position in which the contact arms bridge the 9 and 0 switch contacts. hen in this position, the circuit from the transformer tap 9 to the conductor 117 may be still traced by way of the 9 switch contact and the main switch arm, but the whole series of small subdivisions of the transformer winding are shunted through the circuit which includes the zero transformer tap, the zero switch contact, the auxiliary switch arm, the conductor 131, resistances 132-129, the main switch arm, the :9 switch contact and the transformer tap JO. 9.

Fig. 9 illustrates the switch after the last step of its cycle of movement has been completed, the main switch arm having been brought back to its normal position, resting on the zero contact, and the auxiliary switch arm resting on the insulation between the zero contact and the 1 switch contact. At this time all of the small subdivisions of winding 110 will have been cut out of circuit and one, or an additional one, of the larger subdivisions cut in.

The controller may be provided with means for preventing the rotation of the secondary switch beyond its last or 90 contact, in which case, should it be desired to restore the electromotive force of the transformer coil 119 to zero, after having cut all the various sections of the auto-transformer 110 into circuit therewith it would be necessary to rotate the switches back by a reverse rotation of the primary switch. In accordance with this invention, however, the restoration of the switches to their positions corresponding to zero potential may be more rap dly affected. To this end the secondary switch may be provided with a resistance or impedance 133 of a magnitude apportioned with respect to the series of larger subdivisions of the transformer 110 just as the resistance 132 is apportioned to the series of smaller subdivisions. The curved cor.- ductor 128 of the secondary switch-may also be made in the form of a ring, having an insulated section 134 corresponding in function with section 131 of the primary switch. According to this construction of the switch, the controller switches may be returned to their zero positions after the switch arms have been advanced to the 90 and 9 contacts, respectively, by a single advance step of the primary switch.

The switch contacts, as well as the conductors 128-131-131, may, if desired, have binding post 135, extendlng through the panel board, and the various conductors from the transformer windings may be connected therewith at the war, as indicated in Fig 2. a

The spindle which carries the switch arm may be mounted in the panel board by means of a bearing member 136, of conducting material, and the conductors from the transformer winding 119 may be connected therewith at the rear of the board in any suitable manner.

The switch arms of the two switches may be insulated from each other in any appropriate manner. To this end the wheels bywhich motion is transmitted'from the primary switch to the secondary switch are indicated as being connected to their respective spindles by means of insulating material, as indicated at 137, Fig. 2.

The number of subdivisions into which the auto-transformer may be divided, the relative number of large subdivisions as compared with the number of small ones, and their relative magnitude, may be varied at the will of the designer in accordance with the results desired, so long as the switch contacts are varied accordingly. As disclosed in Fig. 1, with nine small subdivisions, each one tenth of the magnitude of a large subdivision, and with ten contacts in the primary switch, each step of advance rotation of the primary switch adds one increment of electromotive force to the controller circuit, since on passing from the 9 contact to the 0 contact, the nine subdivisions controlled by the primary switch are cut out of circuit, and an additional subdivision, corresponding in magnitude to ten small subdivisions, iscut in.

If it is desired to so divide the auto-transformer as to effect a control in steps of percentages from one to one hundred. all that is necessary is to include ten of the small subdivisionsinstead of nine, and provide the primary switch with eleven contacts instead of ten. V hen so modified the movement of the primary switch from its 10 contact to its 0 contact would be an idle step since it would merely cut out ten small subdivisions of the transformer winding and cause the secondary switch to introduce a single subdivision equal in magnitude to the ten small ones.

Fig. 10 illustrates the invention embodied as a controller for a three phase alternating current transformer. As thus disclosed 150, 151, 152 may be regarded as the main con ductors of a three phase power circuit energized by any appropriate source of electromotive force. Connected between these terminals are three auto-transformers 153, 154, 155. Foreach of these transformers there may be provided a multi-switch controller, those herein disclosed each comprising two switches, a primary switch and a secondary switch, P P P S S S Each pair of switches may be connected to the corresponding auto-transformer exactly as switches P and S of Fig, 1 are connected the primary windings 119 of the trans former 120. The secondary windings 162,

- 163, 164 of these transformers may be connected to the conductors 165, 166, 167 of a three phase transmission circuit 'as indicated. v

In the embodiment of the invention as illustrated in Fig. 10 the three primary switches are provided with means for causing the contact arms to move to correspondingswitch contacts in unison. The secondary switches are likewise provided with means for causing their contact arms to move to corresponding contacts in unison, and means is also provided whereby, on movement of the contact arms of the primary switches from their last contact to their zero contacts, the arms of the secondary switches will all be advanced one step, One means for accomplishing this is illustrated in Fig. 12. As there disclosed,- the three primary switches a re mounted on the face of a switchboard structure, showing in part front elevation in Fig. 11, and the three secondary switches are mounted on the rear of said structure.

Each of the primary switches is mounted on a spindle having fast thereto a beveled gear 168 and these beveled gears are in meshed relation with the beveled gears 169 on a common driving shaft 170, which may be mounted at the back of the panel 171 in bearings 172. In like manner, the secondary switches S S S -may be mounted at the rear face of the panel board 173 on spindles having fast thereto beveled gears 174 in meshed relation with beveled gears 175, secured to a common driving shaft 17 6 mounted in bearingsl77 carried by the panel board structure. The spindle 178 of the priniary switch P may be provided with a suitable crank 179 by which it may be rotated and means comprising a driving element 181 secured to the spindle 178 and a driven element 182 secured to the spindle 180 may be provided whereby at each completion of a rotation of the primary switch P and of switches P and P connected therewith, the switch S and switches S and S connected therewith will be advanced one step. This driving connection may be in every respect similar to the gears 122, 125 illustrated in Fig. 1. By the operation of these switches the difference of potential bev tween the conductors of the different phases may be controlled as in the case of the single phase controller of Fig. 1.

In the modification disclosed in Figs. 10, 11, 12 the various switches may be insulated each from the other by building up the shafts 170, 176 of sections separated each driven by a motor, as indicated in Fig. 13..

In the particular form illustrated 185 is the motor having a driving shaft 186 carrying a worm 187 to drive a worm wheel 188 to which is connected, by means of shaft 189, a driving gear 190 having driving teeth 191 to engage notches 192 in a gear. 193 fast to a shaft 194, to which is secured the driving gear 195 which, as here disclosed, may be regarded as being connected to the primary switch of the invention as disclosed in either Fig. 1 .or Fig. 10. The gear 196, driven by a tooth 197 of gear 195, may be regarded as being connected to the secondary switch of the invention as disclosed in either of the last mentioned figures. Secured for rotation with the worm wheel 188 is a circuit breaker comprising a ring 197', consisting of alternating sections of insulating material 198 and conducting material 199.

The motor may be of the alternating current type as, for example, a three phase induction motor, supplied with energy by conductors 200, 201, 202 respectively connected with any suitable source of electromotive force. The conductor 202 may be connected directly with the motor as indicated. Conductors 200, 201 may be connected with the terminals 203, 204 of a starting switch 205 through a reversing switch 206. The circuit from the starting switch 205 to the motor is completed by conductors 207, 208. In order to effect a movement of the primary switch of the controller in either direction allthat is necessary is to bring reversing switch 206 into contact with one or other of its two sets of terminals, depending upon whether it is desired to move the switch in an advance or retrograde direction, and then close the starting switch 205. It will be apparent, however, that unless additional means is provided the opening of the switch 205 might cause the motor to stop at a time when the switch arm of the controller switch rests between two contacts. In order to prevent this and to cause the switch to be stopped only when the switch arm is centered upon a contact there are provided, in accordance with the invention herein disclosed, shunt connections around the terminals of the starting switch, to be controlled by a movable part of the switching device. One of these connections comprises conductor 209, brushes 210, 211, and conductor 212. The

other shunt connection comprises a conductor 213, brushes 214, 215 and conductor T be du ng nd insulating sections switches have been moved from their normal positions, in which the switch arms are centered upon switch contacts, the movement will be continued until the switch arm of each switch rests upon and is in centered relation with a contact. This will be true even though the starting switch 205 may be opened, since the terminals 203, 204 of said switch will still be connected with the motor through the shunt connections 209, 212, 218, 216, the brushes 210, 211, 214;, 215 and the conducting sections 199 of the ring 197. After the tooth 191 of the wheel 190 has moved clear of the notch 192 in wheel 193, the brushes 210, 211, 214:, 215 will be separated by insulating sections 198, so as to break the motor circuit and permit the motor to come to rest.

The invention is not dependent upon the use of a motor of any particular type. If, for example, conductor 202 leading to motor be ignored this figure may be regarded as illustrating a motor driven by a continuous current without other change, the two re maining conductors being those of the armature circuit. Nor is the invention limited to the specific type of shunt controlling device herein disclosed but is intended to include any equivalent means controlled by some moving part of the switch mechanism for causing the motor to continue its operation until the switch arm is properly centered over a switch contact.

It will be apparent that the controller of Fig. 1 is not limited in its application to the particular embodiment disclosed, but is equally adapted to many other uses, as, for example, to control a low potential distribution system connected with the switch terminals 101, 102 and receiving energy from a high potential power circuit connected with the winding 121, regarded as a primary winding of .the transformer 120. It will also be apparent that the controller would be adapted to vary the voltage in a low potential system having its secondary winding corresponding with winding 121 of transformer 120. Similar modifications of the form of the invention disclosed in Fig. 10 would also suggest themselves to one skilled in the art. In other words, transformers 159, 160, 161 may be such as to either increase or decrease the potential in the circuit 165, 166, 167 and the last mentioned circuit may be either the power circuit or the distribution circuit.

The controller is also well adapted for use in the testing of transformers in which case the transformer to be tested may be substituted for the transformer 12d of Fig. 1 or for the transformers 159, 160, 161 of Fig. 10.

As herein disclosed the mechanical details of the switches and switch mechanisms are intended to be conventional and for the purpose of illustration only, since the invention does not depend upon the structural details of these parts. Any appropriate switch mechanism, including contacts, binding posts, brushes, etc., of the known art, may be made use of.

\Vhat I claim is 1. An electric controller comprising a primary switching device and a secondary switching device, each movable to a plurality of successive positions of varying controlling effect, said primary device being capable of repeating its cycle of movements, means for causing said secondary device to advance one step at each advance movement of the primary device through the step which completes its cycle of movements, and means for maintaining said secondary device locked against movement except when being moved by said primary device.

2. An electric controller comprising a pri mary switching device and a secondary switching device, each movable to a plurality of successive positions of varying control ling effect, said primary device being capable of repeating its cycle of movements, means for causing said secondary device to advance one step at each advance movement of the prima y device through the step which completes cycle of movements, said means being such as to also move said secondary device back one step on each backward movement of said primary device through said last step of its cycle of movements, and means for maintaining said secondary device locked against movement ex cept when being moved by said primary device.

3. An electric controller comprising a primary switching device and a secondary switching device, each. movable to a plurality of successive positions of varying controlling etl'ect, said primary device being capable of repeating its cycle of movements means controlled by said primary device for causing said secondary device to advance one step at each advance movement of the primary device through the step which completes its cycle of movements, and means for maintaining said secondary device locked against movement except when being moved by said primary device.

4. An electric controller comprising a primary switching device and a secondary switching device, each movable to a plurality of successive positions of varying controlling effect, said primary device being capable of repeating its cycle of movements, means for causing said secondary device to advance one step at each advance movement of the primary device through the step which completes its cycle of movements, and means for maintaining said secondary device locked against movement except when being moved by said primary device, the controlling effect at different positions of each device beingequal to the sum of the increments of the' whole cycle of movement of the primary device.

5. An electric controller for the circuits of a polyphase electric system comprising, for each phase, a primary switching device and a secondary switching device, each movable to a plurality of successive positions of varying controlling effect, each of said primary devices being capable of repeating its cycle of movements, means for causing said primary devices to move to their corresponding positions concomitantly, means for causing said secondary devices to move to their corresponding positions concomitantly, and means for causing said secondary de vices to concomitantly advance one step at each advance movement ofthe primary devices through the steps which complete their respective cycles.

6. An electric controller for the circuits of a polyphase electric system comprising, for each phase, a primary'switching device and a secondary switching device, each-movable to a plurality of successive positions of varylng controlling effect, each of said primary devices being capable of repeating its cycle of movements, a train of gearing for causing said primary devices to move to their corresponding positions concomitantly, a train of gearing for causing said secondary devices to move to their corresponding positions concomitantly, and a single driving element connected for movement by said first-mentioned train of gearing and caused thereby to intermittently engage a driven element connected with said secondary train of gearing and thereby cause'said secondary devices to concomitantly advance one step at each advancemovement of the primary devices through the steps which complete their respective cycles.

7. An electric controller comprising a series of spaced contact elements to be maintained at different degrees of electric potential, the, difference of potential between one pair of adjacent elements being materially greater than that between any other pair, a switch having spaced arms to move in succession from element to element, said arms being so spaced as to alternately connect a pair of said elements and then be connected by an element, two shunts having current limiting capacities of difierent magnitudes, and means for selectively connecting said arms through one or the other of said shunts when connecting a pair of said contacts, the shunt of greater current-limiting capacity being selected only when the pair of elements of greatest difference oi potential is connected by said arms. I

8. An electric controller comprising a series of spaced contact elements to be maintained at different degrees of electric potential, the differences between successive elements from the first to the last of the series being substantially equal in degree and of like character, the difi'erence between the last and the first being therefore of opposite character and equal in magnitude to the sum of the differences between their adjacent elements of the series, a switch having spaced arms to move in succession from element to element from the first to the last and from the last directly to the first, said arms being so spaced as to alternately connect a pair of said elements and then be connected by an element, two shunts having current-limiting capacities of different magnitudes, means for connecting said arms through the shunt of greater current-limiting capacity when connecting the last element of the series with the first and for connecting said arms through the other of said shunts when connecting any other pair of adjacent elements. 1

In witness whereof I have hereunto signed my name.

JOHN L. SOHERMERHORN. 

